A method, system, apparatus and readable storage medium for calibrating colorimeter stimulus values

Abstract

The application discloses a colorimeter stimulus value calibration method, system, device and readable storage medium, which is used for improving the color measurement accuracy of a colorimeter. The method comprises the following steps: establishing a standard stimulus value database; establishing a to-be-calibrated colorimeter database; dividing the to-be-calibrated colorimeter database into a plurality of hexahedrons in a spatial coordinate system; obtaining test tristimulus values of a test color through the to-be-calibrated colorimeter; obtaining a target hexahedron to which the test tristimulus values belong from the plurality of hexahedrons; calculating a relative deviation stimulus value of the test tristimulus values based on all axial directions of the target hexahedron in the spatial coordinate system; obtaining corresponding standard stimulus values from the standard stimulus value database according to each endpoint of the target hexahedron; performing preliminary calibration on the relative deviation stimulus value by using a trilinear interpolation method and the standard stimulus values, so as to obtain intermediate stimulus values; and performing brightness calibration on the intermediate stimulus values, so as to obtain target stimulus values.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of colorimeter calibration, and particularly relates to a colorimeter stimulus value calibration method, system, device and readable storage medium. BACKGROUND

[0002] A colorimeter is an instrument for measuring the color parameters of an object, widely used in printing, textiles, display devices and other fields. The measurement results of a colorimeter are usually expressed in terms of three stimulus values (X, Y, Z), and the accuracy directly affects the effect of color management. However, due to differences in light sources, sensors, optical systems and other factors, the measurement results of a colorimeter may be biased, resulting in inaccurate or inconsistent measurement data.

[0003] Existing colorimeter calibration methods mostly use standard color cards for calibration, but the color range of standard color cards is limited and cannot cover all actual measurement scenarios. SUMMARY

[0004] To solve the above technical problems, the present application provides a colorimeter stimulus value calibration method, system, device and readable storage medium, which is used to improve the measurement accuracy of a colorimeter for color.

[0005] The technical solutions provided in the present application are described below:

[0006] The first aspect of the present application provides a colorimeter stimulus value calibration method, comprising:

[0007] Testing the standard stimulus values corresponding to each color block of the standard color card under each standard light source, and establishing a standard stimulus value database according to the standard stimulus values;

[0008] Testing the stimulus values corresponding to each color block of the standard color card under each standard light source of the colorimeter to be calibrated under the same environment, and establishing a colorimeter to be calibrated database;

[0009] Dividing the colorimeter to be calibrated database into a plurality of hexahedrons in a spatial coordinate system;

[0010] Obtaining the test tristimulus values of the test color through the colorimeter to be calibrated;

[0011] Obtaining the target hexahedron to which the test tristimulus values belong from the plurality of hexahedrons;

[0012] Calculating the relative deviation stimulus values of the test tristimulus values based on the target hexahedron in all axes of the spatial coordinate system;

[0013] Obtaining the corresponding standard stimulus values from the standard stimulus value database according to each endpoint of the target hexahedron;

[0014] Calibrating the intermediate stimulus values to obtain target stimulus values by brightness calibration.

[0015] Calibrating the intermediate stimulus values to obtain target stimulus values by brightness calibration.

[0016] Optionally, the brightness calibration of the intermediate stimulus values to obtain target stimulus values comprises:

[0017] Obtaining standard brightness values from the standard stimulus value database;

[0018] Obtaining test brightness values from the database of the colorimeter to be calibrated;

[0019] Establishing a linear relationship between the standard brightness values and the test brightness values by least square method to obtain a calibration factor;

[0020] Calibrating the intermediate stimulus values by the calibration factor to obtain target stimulus values.

[0021] Optionally, the establishing of the linear relationship between the standard brightness values and the test brightness values by least square method to obtain a calibration factor comprises:

[0022] Establishing a linear relationship between the standard brightness values Y std_i and the test brightness values Y test_i , and the linear relationship is expressed as follows:

[0023] ;

[0024] Wherein, k is the calibration factor;

[0025] Solving the calibration factor k by least square method to obtain the following formula:

[0026] ;

[0027] Wherein, parameter i is the serial number of the color block in the standard color card, Y std_i and Y test_i are Y values of the three stimulus values corresponding to the i-th color block in the standard stimulus value database and the database of the colorimeter to be calibrated respectively.

[0028] Optionally, the calculation of the test three stimulus values is based on the relative deviation stimulus values of the target hexahedron in all axial directions of the spatial coordinate system, and the relative deviation stimulus values are expressed as {U, V, W}, and the calculation method of the relative deviation stimulus values is as follows:

[0029]

[0030] , , ;​

[0031] wherein the test tristimulus value is {X test , Y test , Z test}, {X test_ijk , Y test_ijk , Z test_ijk} is an end point coordinate of the target hexahedron, i, j, k is an end point unit coordinate, i, j, k is 0 or 1, and {X test_000 , Y test_000 , Z test_000} is an origin point coordinate of the target hexahedron.

[0032] Optionally, the preliminary calibration of the relative deviation tristimulus value by using the trilinear interpolation method and the standard tristimulus value to obtain an intermediate tristimulus value comprises:

[0033] The intermediate tristimulus value is {X', Y', Z'}, and the calculation method of the intermediate tristimulus value is:

[0034] ;

[0035] ;

[0036] ;

[0037] wherein {X std_ijk , Y std_ijk , Z std_ijk} is a standard tristimulus value, i, j, k is an end point unit coordinate, i, j, k is 0 or 1, and {U, V, W} is a relative deviation tristimulus value.

[0038] Optionally, the obtaining of the target hexahedron to which the test tristimulus value belongs from the plurality of hexahedrons comprises:

[0039] determining eight tristimulus value data closest to the test tristimulus value from the database of the colorimeter to be calibrated;

[0040] determining a target hexahedron with the eight tristimulus value data as end points.

[0041] Optionally, the dividing of the database of the colorimeter to be calibrated into a plurality of hexahedrons in a spatial coordinate system comprises:

[0042] connecting two adjacent tristimulus values in the database of the colorimeter to be calibrated in a spatial coordinate system to obtain a tristimulus value connection line;

[0043] obtaining all tristimulus value connection lines to divide the spatial coordinate system into a plurality of hexahedrons.

[0044] The second aspect of the application provides a colorimeter stimulus value calibration system, comprising:

[0045] A first establishing unit is configured to test standard stimulus values corresponding to each color block of a standard color card under each standard light source, and establish a standard stimulus value database according to the standard stimulus values;

[0046] A second establishing unit is configured to test stimulus values corresponding to each color block of a standard color card under each standard light source by a colorimeter to be calibrated under the same environment, and establish a colorimeter-to-be-calibrated database;

[0047] A dividing unit is configured to divide the colorimeter-to-be-calibrated database into a plurality of hexahedrons in a spatial coordinate system;

[0048] A testing unit is configured to acquire test tristimulus values of a test color by the colorimeter to be calibrated;

[0049] A first acquiring unit is configured to acquire a target hexahedron to which the test tristimulus values belong from the plurality of hexahedrons;

[0050] A calculating unit is configured to calculate a relative deviation stimulus value of the test tristimulus values based on the target hexahedron in all axial directions of the spatial coordinate system;

[0051] A second acquiring unit is configured to acquire corresponding standard stimulus values from the standard stimulus value database according to each endpoint of the target hexahedron;

[0052] A preliminary calibration unit is configured to preliminarily calibrate the relative deviation stimulus value by using a trilinear interpolation method and the standard stimulus values, to obtain intermediate stimulus values;

[0053] A brightness calibration unit is configured to perform brightness calibration on the intermediate stimulus values, to obtain target stimulus values.

[0054] Optionally, the brightness calibration unit is further configured to:

[0055] acquire a standard brightness value from the standard stimulus value database;

[0056] acquire a test brightness value from the colorimeter-to-be-calibrated database;

[0057] establish a linear relationship between the standard brightness value and the test brightness value by a least square method, to obtain a calibration factor;

[0058] calibrate the intermediate stimulus values by the calibration factor, to obtain target stimulus values.

[0059] Optionally, the brightness calibration unit is further configured to:

[0060] establish the standard brightness value Y std_iand the test luminance value Y test_i The linear relationship is expressed as follows:

[0061] ;

[0062] wherein k is a calibration factor;

[0063] The calibration factor k is solved by least square method, and the following formula is obtained:

[0064] ;

[0065] wherein i is the serial number of the color block in the standard color card, the calibration factor is a luminance scaling coefficient, Y std_i and Y test_i are Y values of the third stimulus values corresponding to the i-th color block in the standard stimulus value database and the colorimeter database to be calibrated respectively.

[0066] Optionally, the computing unit is further configured to:

[0067] The relative deviation stimulus value is represented as {U, V, W}, and the relative deviation stimulus value is calculated as follows:

[0068] , , ;

[0069] wherein the test third stimulus value is {X test , Y test , Z test}, {X test_ijk , Y test_ijk , Z test_ijk} is the end point coordinate of the target hexahedron, i, j, k is the end point unit coordinate, i, j, k takes 0 or 1, and {X test_000 , Y test_000 , Z test_000} is the origin coordinate of the target hexahedron.

[0070] Optionally, the preliminary calibration unit is further configured to:

[0071] The intermediate stimulus value is {X’, Y’, Z’}, and the calculation method of the intermediate stimulus value is:

[0072] ;

[0073] ;

[0074] ;

[0075] wherein {X std_ijk , Ystd_ijk , Z std_ijk} is a standard stimulus value, i, j, k is an end point unit coordinate, i, j, k takes 0 or 1, {U, V, W} is a relative deviation stimulus value.

[0076] Optionally, the first acquisition unit is further configured to:

[0077] determining eight tristimulus value data closest to the test tristimulus value from the database of the colorimeter to be calibrated;

[0078] determining a target hexahedron with the eight tristimulus value data as end points.

[0079] Optionally, the division unit is further configured to:

[0080] connecting two tristimulus values adjacent to each other in the database of the colorimeter to be calibrated in a spatial coordinate system to obtain a stimulus value connection line;

[0081] obtaining all stimulus value connection lines, and dividing the spatial coordinate system into a plurality of hexahedrons.

[0082] The third aspect of the present application provides a colorimeter stimulus value calibration device, the device comprising:

[0083] a processor, a memory, an input / output unit, and a bus;

[0084] the processor is connected with the memory, the input / output unit, and the bus;

[0085] the memory stores a program, and the processor invokes the program to execute the method of the first aspect and any optional aspect of the first aspect.

[0086] The fourth aspect of the present application provides a computer readable storage medium, the computer readable storage medium stores a program, and the program executes the method of the first aspect and any optional aspect of the first aspect when executed on a computer.

[0087] As can be seen from the above technical solutions, the present application has the following advantages:

[0088] The present application forms a calibration mapping reference by establishing a standard stimulus value database and a database of a colorimeter to be calibrated, and calibrates the colorimeter measurement value (test tristimulus value) by using a trilinear interpolation method. The trilinear interpolation method for calibrating the colorimeter does not need to calibrate each color (such as a non-WRGB picture) individually, but can cover a wide range of colors in one calibration, thereby significantly improving the calibration efficiency and measurement accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0089] In order to more clearly illustrate the technical solutions in the present application, the drawings needed in the embodiments will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort.

[0090] Figure 1 An embodiment flowchart of a colorimeter stimulus value calibration method in the present application;

[0091] Figure 2 Another embodiment flowchart of a colorimeter stimulus value calibration method in the present application;

[0092] Figure 3 An embodiment structure diagram of a colorimeter stimulus value calibration system in the present application;

[0093] Figure 4 An embodiment structure diagram of a colorimeter stimulus value calibration device in the present application. DETAILED DESCRIPTION

[0094] It should be noted that the colorimeter stimulus value calibration method provided by the present application can be applied to a terminal, a system, and a server. For example, the terminal can be a smart phone or a computer, a tablet computer, a smart television, a smart watch, a portable computer terminal, or a desktop computer. For convenience of description, the terminal is taken as an example in the present application.

[0095] The technical solutions in the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present application.

[0096] Please refer to Figure 1 The present application first provides an embodiment of a colorimeter stimulus value calibration method, which comprises the following steps:

[0097] S101, test the standard stimulus value corresponding to each color block of the standard color card under each standard light source, and establish a standard stimulus value database according to the standard stimulus value;

[0098] The standard light source refers to a light source conforming to international standards (such as CIE standards), which has a specific color temperature and spectral distribution, and is used to simulate different lighting conditions.

[0099] A standard color chart contains multiple color patches covering a wide range of colors. Each color patch of a standard color chart has a determined tristimulus value under a standard light source as a reference for calibration.

[0100] A color patch refers to a single color area on a standard color chart with specific color and optical properties, usually represented by tristimulus values (X, Y, Z).

[0101] Where X is the first tristimulus value in the CIE XYZ color space, representing the weighted contribution of color in the red and green spectral regions, related to hue and saturation; Y is the second tristimulus value in the CIE XYZ color space, representing the brightness or lightness of the color, directly corresponding to the perception of light intensity by the human eye; Z is the third tristimulus value in the CIE XYZ color space, representing the weighted contribution of color in the blue spectral region, related to hue and saturation. That is, Z together with X defines the chromaticity properties of the color, complementing the information of Y to fully describe the color.

[0102] CIE XYZ color space is a standard color space defined by the International Commission on Illumination (CIE), which is based on the trichromatic stimulus theory of the human visual system, and uses three parameters (X, Y, Z) i.e. tristimulus values to represent colors, for quantifying and describing all visible colors perceived by the human eye.

[0103] Standard tristimulus values are the color tristimulus values (X std , Y std , Z std ) of each color patch on a standard color chart measured by a standard reference instrument, representing the spectral properties of the color.

[0104] The standard tristimulus value database is a structured data set that stores the tristimulus values (X std , Y std , Z std ) of each color patch on a standard color chart measured by a standard reference instrument under multiple standard light sources. The data structure stored in the standard tristimulus value database at least contains the following information: 1. Standard light source data 2. Color patch number on the standard color chart 3. Tristimulus values corresponding to data 1 and data 2.

[0105] Specifically, when the light source is m and the color patch is i, one piece of data in the standard tristimulus value database is recorded as {light source m, color patch i, X std_mi , Y std_mi , Z std_mi}.

[0106] S102, test the corresponding tristimulus values of each color patch on the standard color chart under each standard light source of the to-be-calibrated colorimeter in the same environment, and establish a to-be-calibrated colorimeter database;

[0107] The same environment refers to the same environment when the standard stimulus value database is established, and the colorimeter to be calibrated is a colorimeter that has not been calibrated.

[0108] Specifically, by using the colorimeter to be calibrated to obtain the three stimulus values corresponding to each color block of the same color card in the same environment, the measurement difference between the colorimeter to be calibrated and the standard reference instrument can be calculated by the difference between the measurement results of the colorimeter to be calibrated and the standard reference instrument. To obtain more accurate measurement difference, the data obtained by the colorimeter to be calibrated and the data obtained by the standard reference instrument should be established through the same structure to obtain a similar database, i.e. the colorimeter to be calibrated database, which is used to store the three stimulus values corresponding to each color block of the same color card obtained by the colorimeter to be calibrated in the same environment.

[0109] Specifically, when the light source is m and the color block is i, one of the data in the colorimeter to be calibrated database is recorded as {light source m, color block i, X test_mi , Y test_mi , Z test_mi}.

[0110] It should be noted that the same environment described in the present application can be established by human beings, such as through a dark box or a dark room to avoid the influence of environmental light on the test process. The specific way to achieve the same environment is not limited here.

[0111] S103, dividing the colorimeter to be calibrated database into a plurality of hexahedrons in a spatial coordinate system;

[0112] Specifically, the actual effective values stored in the colorimeter to be calibrated database are the three stimulus values obtained by the colorimeter to be calibrated when measuring the standard color card, and the color block and light source data are used for indexing and marking.

[0113] The spatial coordinate system is the CIE XYZ color space, i.e. positioning in the spatial coordinate system through the three stimulus values, and each three stimulus value data in the colorimeter to be calibrated database can find a unique point in the spatial coordinate system. The purpose of dividing the hexahedron is to determine at least eight three stimulus value points in the spatial coordinate system. In actual situations, the number of colors possessed by the standard color card is much larger than eight colors, so in actual situations, there is more than one hexahedron determined by the three stimulus value points in the spatial coordinate system according to the colorimeter to be calibrated database.

[0114] S104, obtaining test three stimulus values of test colors by the colorimeter to be calibrated;

[0115] Specifically, the test color is a random color, which can be a color on a standard color card or a random natural color. An environment for obtaining the test color needs to meet the conditions of a standard light source used in a standard stimulus value database, so as to ensure that an effective standard data can be obtained from the standard stimulus value database in a subsequent calibration process.

[0116] S105, obtaining a target hexahedron to which the test tristimulus value belongs from the plurality of hexahedrons;

[0117] Specifically, a falling point of the test tristimulus value in a spatial coordinate system is determined through the test tristimulus value (X test , Y test , Z test ), and a target hexahedron to which the test tristimulus value belongs is determined through eight tristimulus values in a database of the to-be-calibrated colorimeter that are closest to the test tristimulus value and adjacent to the test tristimulus value.

[0118] S106, calculating a relative deviation stimulus value of the test tristimulus value based on the target hexahedron in all axial directions of the spatial coordinate system;

[0119] Because the test color does not necessarily exist on a standard color card and because of color measurement deviation caused by environmental factors, the test tristimulus value can not coincide with any point in the spatial coordinate system. After the target hexahedron to which the test tristimulus value belongs is determined, a new coordinate system is established according to the target hexahedron, with a lower left corner of the hexahedron as an origin (0, 0, 0), a relative position of the test tristimulus value and the origin of the target hexahedron in axial directions (X axis, Y axis and Z axis) is calculated, and a relative deviation stimulus value is obtained.

[0120] S107, obtaining corresponding standard stimulus values from the standard stimulus value database according to each end point of the target hexahedron;

[0121] Specifically, the standard stimulus value database and the database of the to-be-calibrated colorimeter are two databases with one-to-one correspondence in data volume and data structure, which are obtained through the same environment, the same standard color card and different colorimeters. Therefore, after the target hexahedron is determined, the standard stimulus value data corresponding to eight end points of the hexahedron can be obtained from the standard stimulus value database through the end points of the target hexahedron.

[0122] S108, performing preliminary calibration on the relative deviation stimulus value using a trilinear interpolation method and the standard stimulus values, to obtain an intermediate stimulus value;

[0123] Specifically, the data in the database of the colorimeter to be calibrated is used to calculate the relative deviation stimulus value, i.e., the color three-stimulus value obtained by testing through the colorimeter to be calibrated. However, because the actual test of the colorimeter to be calibrated and the standard reference instrument has deviation, after the relative deviation stimulus value of the color to be tested is determined, it still needs to be calibrated through the standard stimulus value to reduce the influence of the measurement deviation of the colorimeter to be calibrated on the actual value of the measured color. The relative deviation stimulus value after preliminary calibration is the intermediate stimulus value.

[0124] S109, performing luminance calibration on the intermediate stimulus value to obtain a target stimulus value.

[0125] Specifically, because the measurement environment for obtaining the test three-stimulus value is random, it may be affected by luminance. In actual situations, the change of luminance is a direct scaling linear relationship, i.e., a simple proportional relationship. In order to determine the proportional coefficient, the accurate luminance value (which can be obtained from the standard stimulus value database) needs to be obtained through the standard reference instrument. The proportional relationship between the standard luminance value and the luminance value (which can be obtained from the database of the colorimeter to be calibrated) obtained by the colorimeter to be calibrated is established, and the proportional relationship is linearly fitted to obtain the calibration parameter. The intermediate stimulus value is calibrated through the calibration parameter to obtain the target stimulus value.

[0126] The embodiment establishes the standard stimulus value database and the database of the colorimeter to be calibrated to form a calibration mapping reference, and uses the trilinear interpolation method to realize the calibration of the colorimeter measurement value (test three-stimulus value). The trilinear interpolation method realizes the calibration of the colorimeter without the need of separate calibration for each color (such as non-WRGB pictures). Once calibration, it can cover a wide range of colors, significantly improving the calibration efficiency and measurement accuracy.

[0127] Please refer to Figure 2 The embodiment of the present application provides another embodiment of the colorimeter stimulus value calibration method, which comprises:

[0128] S201, testing the standard stimulus value corresponding to each color block of the standard color card under each standard light source, and establishing a standard stimulus value database according to the standard stimulus value;

[0129] S202, testing the stimulus value corresponding to each color block of the standard color card under each standard light source through the colorimeter to be calibrated in the same environment, and establishing a database of the colorimeter to be calibrated;

[0130] The steps S201 to S202 in the embodiment are similar to the steps S101 to S102 in the foregoing embodiment, and will not be described here.

[0131] S203, connecting two three-stimulus values adjacent to each other in the database of the colorimeter to be calibrated in a spatial coordinate system to obtain a stimulus value connection line;

[0132] The two adjacent three-stimulus values determine two unique points in the spatial coordinate system. In actual cases, there are more than one point adjacent to a three-stimulus value in the spatial coordinate system, and thus the three-stimulus value in the spatial coordinate system will generate multiple connection lines with all the adjacent points.

[0133] S204, obtaining all the connection lines of the three-stimulus values, and dividing the spatial coordinate system into multiple hexahedrons.

[0134] According to the description of step S203, because the number of connection lines of the three-stimulus values is not unique, when all the three-stimulus values in the spatial coordinate system generate connection lines with adjacent three-stimulus values, the spatial coordinate system will be divided into multiple hexahedrons.

[0135] S205, obtaining a test three-stimulus value of a test color by the colorimeter to be calibrated;

[0136] Step S205 in the embodiment is similar to step S104 in the foregoing embodiment, and thus will not be described here.

[0137] S206, determining eight three-stimulus value data closest to the test three-stimulus value from the database of the colorimeter to be calibrated;

[0138] In actual cases, the information stored in the database of the colorimeter to be calibrated is the color of a standard color card obtained by the colorimeter to be calibrated. When the test three-stimulus value is determined, the eight three-stimulus values closest to the test three-stimulus value in the spatial coordinate system are determined by determining the adjacent points of the test three-stimulus value in the database of the colorimeter to be calibrated. The reason for selecting eight adjacent points is that eight points can determine a limited hexahedron space in the spatial coordinate system, and because all the end points of the limited hexahedron space have known characteristics and parameters, the correct parameters of the test three-stimulus value in the spatial coordinate system can be calculated based on the mathematical characteristics of the hexahedron in the spatial coordinate system.

[0139] S207, determining a target hexahedron with the eight three-stimulus value data as end points.

[0140] According to the description of step S206, the hexahedron composed of the eight three-stimulus value data closest to the test three-stimulus value in the database of the colorimeter to be calibrated is the target hexahedron.

[0141] S208, calculating the relative deviation three-stimulus value of the test three-stimulus value based on the target hexahedron in all the axial directions of the spatial coordinate system.

[0142] The relative deviation stimulus value is represented as {U, V, W}, and the relative deviation stimulus value is calculated as follows:

[0143] , , ;

[0144] wherein the test tristimulus value is {X test , Y test , Z test}, {X test_ijk , Y test_ijk , Z test_ijk} is the end point coordinate of the target hexahedron, i, j, k is the end point unit coordinate, i, j, k takes the value of 0 or 1, and {X test_000 , Y test_000 , Z test_000} is the origin coordinate of the target hexahedron.

[0145] Specifically, the eight end points of the target hexahedron are denoted as {p1, p2, p3, p4, p5, p6, p7, p8}, wherein the tristimulus value of p1 is denoted as {X test_000 , Y test_000 , Z test_000}, and according to the actual position of the target hexahedron, the representation of the coordinates corresponding to the remaining 7 points is obtained as follows: {X test_100 , Y test_100 , Z test_100}, {X test_110 , Y test_110 , Z test_110}, {X test_111 , Y test_111 , Z test_111}, {X test_010 , Y test_010 , Z test_010}, {X test_011 , Y test_011 , Z test_011}, {X test_001 , Y test_001 , Z test_001}, {X test_101 , Y test_101 , Z test_101}.

[0146] The calculation method of the relative deviation stimulus value {U, V, W} is to calculate the relative position of the test tristimulus value {X test , Y test , Z test} and the p1 point (origin) of the target hexahedron in the axial direction (X axis, Y axis and Z axis), i.e. the test tristimulus value based on the origin coordinate is {X test_100 , Ytest_100 test_100} of the X-axis direction, coordinates of the Y-axis direction and coordinates of the Z-axis direction. test_010 test_010 test_010 test_001 test_001 test_001 std_ijk std_ijk std_ijk

[0147] The relative deviation stimulus value calculated in the above manner is denoted as {U, V, W}, and {U, V, W} ∈ [0, 1], which represents the normalized coordinates of the test three-stimulus value in the target hexahedron and reflects the relative distance thereof from the eight vertices.

[0148] S209, acquiring corresponding standard stimulus values from the standard stimulus value database according to each endpoint of the target hexahedron;

[0149] The step S209 in the embodiment is similar to the step S107 in the foregoing embodiment, and details are not repeated here.

[0150] S210, using a trilinear interpolation method and the standard stimulus values to preliminarily calibrate the relative deviation stimulus value to obtain an intermediate stimulus value;

[0151] The intermediate stimulus value is {X’, Y’, Z’}, and the calculation method of the intermediate stimulus value is:

[0152]

[0153]

[0154]

[0155] std_ijk std_ijk std_ijk

[0156] Specifically, the intermediate stimulus value {X’, Y’, Z’} calculation formula is expanded as follows (taking the calculation of X’ as an example, the expansion of Y’ and Z’ is similar to the expansion result of X’):

[0157]

[0158] According to the above expansion, the X’ value of the intermediate stimulus value can be obtained. Similarly, the Y’ value and the Z’ value of the intermediate stimulus value can be obtained.

[0159] ​​​​​​​​​​​Specifically, trilinear interpolation is a mathematical method for estimating point values ​​in three-dimensional space (such as the CIE XYZ color space or spatial coordinate system). It primarily involves estimating point values ​​given a three-dimensional mesh cell (a target hexahedron with eight known vertices) using the known values ​​of its eight vertices (standard stimulus values ​​{X...}). std_ijk Y std_ijk Z std_ijk}) and the relative position of the target point within the grid (relative deviation stimulus value {U,V,W}), calculate the value of the target point (intermediate stimulus value {X',Y',Z'}).

[0160] Thus, in this embodiment, the standard stimulus values ​​obtained from the standard stimulus value database obtained by the standard reference instrument have completed the basic calibration of the tristimulus values ​​obtained by the colorimeter to be calibrated, and intermediate stimulus values ​​have been obtained.

[0161] S211. Obtain standard brightness values ​​from the standard stimulus value database;

[0162] In practice, the measurement deviation of the colorimeter to be calibrated (sensor response, gain error, etc.) causes the brightness value measured by the colorimeter to be calibrated to be inconsistent with the brightness value measured by the standard reference instrument. Therefore, brightness calibration is required for intermediate stimulus values. Thus, it is necessary to obtain the standard brightness value (the brightness value is the Y value in the tristimulus value) from the standard stimulus value database and determine the brightness calibration scaling factor with the parameter value obtained by the colorimeter from the colorimeter database to be calibrated.

[0163] S212. Obtain the test luminance value from the colorimeter database to be calibrated;

[0164] After determining the standard stimulus value database, it is also necessary to obtain the test luminance values ​​of the colorimeter database to be calibrated. Since the databases are established under the same standard color chart and the same environment, the data in the standard stimulus value database and the colorimeter database to be calibrated have a one-to-one correspondence.

[0165] S213. Establish a linear relationship between the standard brightness value and the test brightness value using the least squares method to obtain the calibration factor;

[0166] Establish the standard luminance value Y std_i and the test brightness value Y test_i The linear relationship is expressed as follows:

[0167] ;

[0168] Where k is the calibration factor;

[0169] The calibration factor k is solved using the least squares method, yielding the following equation:

[0170] .

[0171] It should be noted that the parameter i in the embodiment is the color block number in the standard color card, and the calibration factor is the luminance scaling coefficient, Y std_i and Y test_i are the Y values of the three stimulus values corresponding to the i-th color block of the standard stimulus value database and the colorimeter database to be calibrated, respectively.

[0172] S214, calibrate the intermediate stimulus value by the calibration factor to obtain a target stimulus value.

[0173] After the scaling coefficient is calculated as the calibration factor, the intermediate stimulus value {X', Y', Z'} is calibrated by a linear relationship formula, and the calibration result is the target stimulus value {X'', Y'', Z''}:

[0174]

[0175] The calibration factor reflects the systematic brightness deviation of the colorimeter, so it will cause proportional influence on other parameters of the three stimulus values. Therefore, after the calibration factor is determined, the scaling of the calibration factor needs to be performed on all the intermediate stimulus value data, in addition, in the spatial coordinate system and the CIE XYZ color space, only one parameter (Y) is calibrated, which will cause hue distortion, so the scaling needs to be performed to keep the chroma unchanged and only adjust the brightness.

[0176] The embodiment realizes efficient and accurate calibration of the colorimeter by establishing a standard and to-be-calibrated database, optimizing hexahedron division, accurately calculating the deviation value, implementing three-linear interpolation and brightness calibration. The interpolation calibration strategy in the spatial coordinate system not only improves the calibration efficiency and accuracy, but also significantly expands the application ability of the colorimeter in complex scenes such as non-WRGB pictures, and provides important technical progress for color measurement technology. In terms of brightness correction, the embodiment further improves the prediction ability of the true stimulus value by introducing the calibration factor, and significantly improves the accuracy and consistency of the colorimeter measurement results.

[0177] The colorimeter stimulus value calibration method in the embodiment of the application is described in detail above, and the colorimeter stimulus value calibration system and device will be described in detail below.

[0178] Please refer to Figure 3 The embodiment of the application provides an embodiment of a colorimeter stimulus value calibration system, which comprises:

[0179] A first establishing unit 301 is configured to test the standard stimulus value corresponding to each color block of the standard color card under each standard light source, and establish a standard stimulus value database according to the standard stimulus value.

[0180] The second establishing unit 302 is configured to test the stimulus values corresponding to each color block of the standard color card under each standard light source of the colorimeter to be calibrated in the same environment, and establish a database of the colorimeter to be calibrated;

[0181] The dividing unit 303 is configured to divide the database of the colorimeter to be calibrated into a plurality of hexahedrons in a spatial coordinate system;

[0182] The testing unit 304 is configured to acquire test tristimulus values of a test color by the colorimeter to be calibrated;

[0183] The first acquiring unit 305 is configured to acquire a target hexahedron to which the test tristimulus values belong from the plurality of hexahedrons;

[0184] The calculating unit 306 is configured to calculate relative deviation stimulus values of the test tristimulus values based on the target hexahedron in all axial directions of the spatial coordinate system;

[0185] The second acquiring unit 307 is configured to acquire corresponding standard stimulus values from the database of standard stimulus values according to each endpoint of the target hexahedron;

[0186] The preliminary calibration unit 308 is configured to preliminarily calibrate the relative deviation stimulus values by using a trilinear interpolation method and the standard stimulus values, to obtain intermediate stimulus values;

[0187] The brightness calibration unit 309 is configured to perform brightness calibration on the intermediate stimulus values, to obtain target stimulus values.

[0188] In this embodiment, the brightness calibration unit 309 is further configured to:

[0189] acquire a standard brightness value from the database of standard stimulus values;

[0190] acquire a test brightness value from the database of the colorimeter to be calibrated;

[0191] establish a linear relationship between the standard brightness value and the test brightness value by using a least square method, to obtain a calibration factor;

[0192] calibrate the intermediate stimulus values by using the calibration factor, to obtain the target stimulus values.

[0193] In this embodiment, the brightness calibration unit 309 is further configured to:

[0194] establish a linear relationship between the standard brightness value Y std_i and the test brightness value Y test_i , and the linear relationship is represented as follows:

[0195] ;

[0196] Wherein, k is a calibration factor;

[0197] Solving the calibration factor k by least square method, the following formula is obtained:

[0198] .

[0199] Wherein, the parameter i in the embodiment is the color block serial number in the standard color card, the calibration factor is the luminance scaling coefficient, Y std_i and Y test_i are the Y values of the three stimulus values corresponding to the i-th color block in the standard stimulus value database and the colorimeter database to be calibrated respectively.

[0200] In the embodiment, the computing unit 306 is further configured to:

[0201] The relative deviation stimulus value is represented as {U, V, W}, and the relative deviation stimulus value is calculated as follows:

[0202] , , ;

[0203] Wherein, the test tristimulus value is {X test , Y test , Z test}, {X test_ijk , Y test_ijk , Z test_ijk} is the end point coordinate of the target hexahedron, i, j, k is the end point unit coordinate, i, j, k takes 0 or 1, and {X test_000 , Y test_000 , Z test_000} is the origin coordinate of the target hexahedron.

[0204] In the embodiment, the preliminary calibration unit 308 is further configured to:

[0205] The intermediate stimulus value is {X’, Y’, Z’}, and the calculation method of the intermediate stimulus value is:

[0206] ;

[0207] ;

[0208] ;

[0209] Wherein, {X std_ijk , Y std_ijk , Z std_ijk} is the standard stimulus value, i, j, k is the end point unit coordinate, i, j, k takes 0 or 1, and {U, V, W} is the relative deviation stimulus value.

[0210] In this embodiment, the first obtaining unit 305 is further configured to:

[0211] determine eight tri-stimulus value data closest to the test tri-stimulus value from the database of colorimeters to be calibrated;

[0212] determine a target hexahedron with the eight tri-stimulus value data as end points.

[0213] In this embodiment, the dividing unit 303 is further configured to:

[0214] connect two tri-stimulus values adjacent to each other in the database of colorimeters to be calibrated in a spatial coordinate system to obtain a connection line of tri-stimulus values;

[0215] obtain all connection lines of tri-stimulus values, and divide the spatial coordinate system into a plurality of hexahedrons.

[0216] In this embodiment, the functions of each unit correspond to the steps in the foregoing Figures 1 to 2 embodiments, and thus will not be described here.

[0217] Please refer to Figure 4 , another embodiment of the colorimeter tri-stimulus value calibration device is provided, which includes:

[0218] a processor 401, a memory 402, an input and output unit 403, and a bus 404;

[0219] The processor 401 is connected with the memory 402, the input and output unit 403, and the bus 404;

[0220] The memory 402 stores a program, and the processor 401 invokes the program to specifically perform operations corresponding to the steps in the method of Figure 1 or Figure 2 , and thus will not be described here.

[0221] The present application also relates to a computer readable storage medium, which stores a program, and when the program runs on a computer, the computer performs operations corresponding to the steps in the method of Figure 1 or Figure 2 , and thus will not be described here.

[0222] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described system, device and unit can refer to the corresponding processes in the foregoing method embodiments, and thus will not be described here.

[0223] In several embodiments provided in the present application, it should be understood that the disclosed system, device and method can be implemented in other manners. For example, the described device embodiments are merely schematic. For example, the division of the units is only a logical function division. There can be another division manner for the actual implementation. For example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections can be indirect couplings or communication connections through some interfaces, devices or units, and can be in electrical, mechanical or other forms.

[0224] The units described as separated components can or can not be physically separated, and the components displayed as units can or can not be physical units, i.e., can be located in one place, or can be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purposes of the embodiments of the present application.

[0225] In addition, each functional unit in the embodiments of the present application can be integrated in one processing unit, or each unit can exist physically as a separate unit, or two or more units can be integrated in one unit. The integrated unit can be implemented in the form of hardware, or in the form of a software functional unit.

[0226] When the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer readable storage medium. Based on such an understanding, the technical solutions of the present application essentially or substantially, or all or part of the technical solutions, can be embodied in the form of a software product. The computer software product is stored in a storage medium, and includes a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the embodiments of the present application. The foregoing storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM, read-only memory), a random access memory (RAM, random access memory), a magnetic disk or an optical disk, and various other media that can store program codes.

Claims

1. A method for calibrating the stimulus value of a colorimeter, characterized in that, The method includes: Test the standard stimulus value corresponding to each color block of the standard color chart under various standard light sources, and establish a standard stimulus value database based on the standard stimulus value; The stimulation values ​​of each color block of the standard color chart corresponding to the colorimeter to be calibrated were tested under various standard light sources in the same environment, and a database of colorimeters to be calibrated was established. The colorimeter database to be calibrated is divided into multiple hexahedrons in a spatial coordinate system; The test tristimulus values ​​of the test color are obtained using the colorimeter to be calibrated; Obtain the target hexahedron to which the test tristimulus value belongs from the plurality of hexahedrons; The test tristimulus values ​​are calculated based on the relative deviation stimulus values ​​of the target hexahedron along all axes of the spatial coordinate system. Based on each endpoint of the target hexahedron, the corresponding standard stimulus value is obtained from the standard stimulus value database; The relative deviation stimulus values ​​were initially calibrated using trilinear interpolation and the standard stimulus values ​​to obtain intermediate stimulus values. The intermediate stimulus value is calibrated for brightness to obtain the target stimulus value.

2. The method according to claim 1, characterized in that, The step of calibrating the brightness of the intermediate stimulus value to obtain the target stimulus value includes: Obtain standard brightness values ​​from the standard stimulus value database; Obtain the test luminance value from the colorimeter database to be calibrated; A linear relationship between the standard brightness value and the test brightness value is established using the least squares method to obtain the calibration factor; The intermediate stimulus value is calibrated using the calibration factor to obtain the target stimulus value.

3. The method according to claim 2, characterized in that, The calibration factor is obtained by establishing a linear relationship between the standard brightness value and the test brightness value using the least squares method, including: Establish the standard luminance value Y std_i and the test brightness value Y test_i The linear relationship is expressed as follows: ； Where k is the calibration factor; The calibration factor k is solved using the least squares method, yielding the following equation: ； Where, parameter i is the color patch number in the standard color chart, Y std_i and Y test_i These are the Y values ​​of the tristimulus values ​​corresponding to the i-th color patch in the standard stimulus value database and the colorimeter database to be calibrated, respectively.

4. The method according to claim 1, characterized in that, The calculation of the test tristimulus value is based on the relative deviation stimulus value of the target hexahedron along all axes of the spatial coordinate system, including: The relative deviation stimulus value is represented as {U,V,W}, and the relative deviation stimulus value is calculated as follows: ， ， ； Wherein, the test tristimulus value is {X} test Y test Z test }, {X test_ijk Y test_ijk Z test_ijk } represents the endpoint coordinates of the target hexahedron, i, j, k are the unit coordinates of the endpoints, and i, j, k take values ​​of 0 or 1, {X test_000 Y test_000 Z test_000 } represents the origin coordinates of the target hexahedron.

5. The method according to claim 4, characterized in that, The preliminary calibration of the relative deviation stimulus value using trilinear interpolation and the standard stimulus value to obtain the intermediate stimulus value includes: The intermediate stimulus values ​​are {X', Y', Z'}, and the intermediate stimulus values ​​are calculated as follows: ； ； ； Among them, {X std_ijk Y std_ijk Z std_ijk } represents the standard stimulus value, i, j, k represents the endpoint unit coordinates, i, j, k takes values ​​of 0 or 1, and {U, V, W} represents the relative deviation stimulus value.

6. The method according to any one of claims 1 to 5, characterized in that, The step of obtaining the target hexahedron to which the test tristimulus value belongs from the plurality of hexahedrons includes: The eight tristimulus values ​​closest to the test tristimulus values ​​are determined from the colorimeter database to be calibrated; The target hexahedron is determined using the eight tristimulus values ​​as endpoints.

7. The method according to any one of claims 1 to 5, characterized in that, The step of dividing the colorimeter database to be calibrated into multiple hexahedrons in a spatial coordinate system includes: Connect two adjacent tristimulus values ​​in the colorimeter database to be calibrated in a spatial coordinate system to obtain the stimulus value connection line; Obtain all stimulus value connecting lines and divide the spatial coordinate system into multiple hexahedrons.

8. A colorimeter stimulus value calibration system, characterized in that, The system includes: The first establishment unit is used to test the standard stimulus value corresponding to each color block of the standard color card under various standard light sources, and to establish a standard stimulus value database based on the standard stimulus value. The second establishment unit is used to test the stimulus values ​​of each color block of the standard color card corresponding to the colorimeter to be calibrated under various standard light sources in the same environment, and to establish a database of colorimeters to be calibrated. A partitioning unit is used to divide the colorimeter database to be calibrated into multiple hexahedrons in a spatial coordinate system; The test unit is used to obtain the test tristimulus values ​​of the test color through the colorimeter to be calibrated; The first acquisition unit is used to acquire the target hexahedron to which the test tristimulus value belongs from the plurality of hexahedrons; The calculation unit is used to calculate the test tristimulus value based on the relative deviation stimulus value of the target hexahedron along all axes of the spatial coordinate system. The second acquisition unit is used to acquire the corresponding standard stimulus values ​​from the standard stimulus value database based on each endpoint of the target hexahedron. The preliminary calibration unit is used to perform preliminary calibration on the relative deviation stimulus value using trilinear interpolation and the standard stimulus value to obtain the intermediate stimulus value; A brightness calibration unit is used to calibrate the brightness of the intermediate stimulus value to obtain the target stimulus value.

9. A colorimeter stimulus value calibration device, characterized in that, The device includes: Processor, memory, input / output units, and bus; The processor is connected to the memory, the input / output unit, and the bus; The memory stores a program, which the processor invokes to perform the method as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium contains a program that, when executed on a computer, performs the method as described in any one of claims 1 to 7.

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